A human spine has three main regions—the cervical, thoracic, and lumbar regions. In a normal spine, the cervical and lumbar regions have a lordotic (backward) curvature, while the thoracic region has a kyphotic (forward) curvature. Such a disposition of the curvatures gives a normal spine an S-shape. Sagittal imbalance is a condition in which the normal alignment of the spine is disrupted in the sagittal plane causing a deformation of the spinal curvature. One example of such a deformity is “flat-back” syndrome, wherein the lumbar region of the spine is generally linear rather than curved. A more extreme example has the lumbar region of the spine exhibiting a kyphotic curvature such that the spine has an overall C-shape, rather than an S-shape. Sagittal imbalance can be a problem in that it is biomechanically disadvantageous and generally results in discomfort, pain, and an awkward appearance in that the patient tends to be bent forward excessively.
Various treatments for sagittal imbalance are known in the art. These treatments generally involve removing at least some bone from a vertebra (osteotomy) and sometimes removal of the entire vertebra (vertebrectomy), in order to reduce the posterior height of the spine in the affected region and recreate lordotic curve. Such procedures are traditionally performed via an open, posterior approach involving a large incision (often to expose multiple spinal levels at the same time) and require stripping of the muscle tissue away from the bone. These procedures can have the disadvantages of a large amount of blood loss, high risk, and a long and painful recovery for the patient. Furthermore, depending upon the patient, multiple procedures, involving both anterior and posterior approaches to the spine, may be required.
The present invention is directed at overcoming, or at least improving upon, the disadvantages of the prior art.